Death is as natural a part of life as is birth; every existence ends in the former as it begins in the latter. Human beings, however, have a natural aversion to addressing death in an open and honest manner. It's as unsuitable for polite conversation as sex and drugs. Movies too often veer into unbearable melodrama when the subject matter encroaches upon the Grim Reaper's territory. Call it the Terms of Endearment syndrome - heap on the manipulation until the audience is drowning in tears. It is refreshing, therefore, to find a film that chronicles the process of accepting death without wallowing in sentimentality. With My Sister's Keeper, director Nick Cassavetes exhibits a degree of restraint that is laudable. The film retains an emotional impact while maintaining a low-key style. It pushes buttons but not to the point of overkill. It is, in short, a rich experience that leaves the viewer in a contemplative mood without feeling used by a director eager to boost Kleenex sales.

I have not read the best-selling novel by Jodi Picoult upon which the screenplay, co-credited to Cassavetes and Jeremy Leven, is based. Judging by the film's structure, which employs flashbacks, a wrap-around voiceover, and various internal monologues throughout, it must have been difficult to get "just right." Credit goes to the director and the writers, who have crafted a screen story that captures the essence of the characters and presents the themes and ideas in a clear, coherent fashion. The actors also deserve a lion's share of the kudos. There's not a weak performance to be found.

The film's "hook" is a stunning declaration by 11-year old Anna Fitzgerald (Abigail Breslin): she does not want to donate a kidney to her older sister, Kate (Sofia Vassileva), who is dying of lymphoma, and she's willing to go to court to validate that decision. Anna was conceived as a "donor baby" - genetically compatible in all ways with Kate so that she could donate blood, bone marrow, and organs to her sister to prolong her life. By age 11, Anna has been poked and prodded with needles and has had bone marrow extracted twice. The prospect of giving her kidney to Kate is terrifying, since the operation is not without danger and it could rob Anna of the capacity to live a "normal" life. So, standing up to her mother, Sara (Cameron Diaz), she decides she wants "medical emancipation," and approaches a lawyer, Campbell Alexander (Alec Baldwin), to take her case. She still wants to live with her family, and still loves her sister, but she wants control of her body. Her brother, Jesse (Evan Ellingson); father, Brian (Jason Patric); and Kate understand and support her, but Sara is angry and hurt.

As the story unfolds, we learn bits and pieces about the various characters and are provided with windows of insight into how Kate's illness has impacted them. (One curious omission, probably as a result of time constraints: Sara's faithful sister, Kelly (Heather Wahlquist), is never properly developed. We never understand what inspires such a selfless devotion to her niece.) Flashbacks tell the story of how Kate's lymphoma was diagnosed and what prompted Sara and Brian to bring Anna into the world; how hairline fissures within the family dynamic became more pronounced because of the potential tragedy in their midst; and how Kate found a way to steal some happiness with Taylor (Thomas Dekker), another cancer patient. The inevitable denouement of My Sister's Keeper is presented in a gentle, dignified manner so unlike the overwrought climax of Terms of Endearment.

The movie raises but does not dwell upon the thorny ethical issue of the rights accorded to a genetically engineered child. This is not, after all, science fiction. As the story progresses, the question of whether Anna is eligible for "medical emancipation" becomes increasingly less important. The focus is upon each character accepting the inevitable where Kate is concerned, with Sara, who has fought the longest and hardest of them all for her daughter, being the last holdout. Her blind devotion to a cause, and her losing sight of the person at the heart of that cause, makes her at times seem like a monster. Cassavetes, however, is mindful of not demonizing Sara, being careful to balance her seeming cruelty with scenes providing insight into her pain and compassion. Love often compels irrational and occasionally ungenerous behavior.

The performances are strong across-the-board. Cameron Diaz, best known for appearing in romantic comedies and lighthearted fare, shows dramatic chops in taking on a role that requires range and depth. Jason Patric's minimalist approach is perfect for Brian, who is caught in the middle of the tug-of-war between his wife and daughter. Abigail Breslin and Sofia Vassileva display a natural bond one might expect from sisters, and there's no hint of artifice or overacting in either performance. Alec Baldwin tones down his tendency toward bombast and delivers a finely tuned portrayal of a lawyer who has a hidden reason to pursue the case with tenacity. Perhaps the most memorable sample of acting comes from Joan Cusack, who provides a heartbreaking interpretation of a bereaved judge. The pain in her eyes, which occasionally pool with tears, cannot fail to move. If there's an Oscar nomination lurking in this film, it should go to Cusack.

The strength of the acting and the modulation of the screenplay transforms what could have been a run-of-the-mill Lifetime disease-of-the-week movie into something more insightful and intelligent. Ultimately, it is sad, but there are moments of joy and enlightenment along the way. My Sister's Keeper does not cheat with a happy ending but, perhaps more importantly, neither does it cheat with something mawkish. By threading that needle, it finds the right mix between emotionality and acumen, a recipe followed by surprisingly too few dramas these days.